eBPF classifier (section "cls_q" in tap_bpf_program.c) is looking for
marked packets whose skb->cb[1] contains an RSS queue number and redirects
those packets to the matched queue.
It is expected that skb->cb[1] has been previously set with a valid RSS
queue number during an eBPF action (section "l3_l4" in tap_bpf_program.c),
however for non-RSS flows skb->cb[1] may contain a random unset value which
can falsely be interpreted as a valid RSS queue.
To avoid this potential error, tap_bpf_program.c has been updated as
follows:
1. After calculating the RSS queue number it is added a unique offset
in order to uniquely identify it as a valid RSS queue number.
2. After matching an RSS queue to a packet - skb->cb[1] is set to 0
Fixes: cdc07e83bb24 ("net/tap: add eBPF program file")
Fixes: aabe70df73a3 ("net/tap: add eBPF bytes code")
Signed-off-by: Ophir Munk <ophi...@mellanox.com>
---
drivers/net/tap/tap_bpf_insns.h | 23 +++++++++++++----------
drivers/net/tap/tap_bpf_program.c | 5 ++++-
2 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/drivers/net/tap/tap_bpf_insns.h b/drivers/net/tap/tap_bpf_insns.h
index c406f78..89873b6 100644
--- a/drivers/net/tap/tap_bpf_insns.h
+++ b/drivers/net/tap/tap_bpf_insns.h
@@ -6,17 +6,20 @@
/* bpf_insn array matching cls_q section. See tap_bpf_program.c file */
struct bpf_insn cls_q_insns[] = {
- {0x61, 1, 1, 52, 0x00000000},
- {0x18, 2, 0, 0, 0xdeadbeef},
+ {0x61, 2, 1, 52, 0x00000000},
+ {0x18, 3, 0, 0, 0xdeadbeef},
{0x00, 0, 0, 0, 0x00000000},
- {0x63, 10, 2, -4, 0x00000000},
- {0x61, 2, 10, -4, 0x00000000},
- {0x07, 2, 0, 0, 0x00000001},
- {0x67, 2, 0, 0, 0x00000020},
- {0x77, 2, 0, 0, 0x00000020},
- {0xb7, 0, 0, 0, 0xffffffff},
- {0x1d, 1, 2, 1, 0x00000000},
+ {0x63, 10, 3, -4, 0x00000000},
{0xb7, 0, 0, 0, 0x00000000},
+ {0x61, 3, 10, -4, 0x00000000},
+ {0x07, 3, 0, 0, 0x7cafe800},
+ {0x67, 3, 0, 0, 0x00000020},
+ {0x77, 3, 0, 0, 0x00000020},
+ {0x5d, 2, 3, 4, 0x00000000},
+ {0xb7, 2, 0, 0, 0x00000000},
+ {0x63, 1, 2, 52, 0x00000000},
+ {0x18, 0, 0, 0, 0xffffffff},
+ {0x00, 0, 0, 0, 0x00000000},
{0x95, 0, 0, 0, 0x00000000},
};
@@ -1685,7 +1688,7 @@ struct bpf_insn l3_l4_hash_insns[] = {
{0x4f, 3, 2, 0, 0x00000000},
{0x67, 3, 0, 0, 0x00000010},
{0x4f, 3, 1, 0, 0x00000000},
- {0x07, 3, 0, 0, 0x00000001},
+ {0x07, 3, 0, 0, 0x7cafe800},
{0x63, 5, 3, 52, 0x00000000},
{0xb7, 7, 0, 0, 0x00000001},
{0xbf, 0, 7, 0, 0x00000000},
diff --git a/drivers/net/tap/tap_bpf_program.c
b/drivers/net/tap/tap_bpf_program.c
index 848c50b..64dcdb8 100644
--- a/drivers/net/tap/tap_bpf_program.c
+++ b/drivers/net/tap/tap_bpf_program.c
@@ -31,7 +31,7 @@
* The queue number is offset by 1, to distinguish packets that have
* gone through this rule (skb->cb[1] != 0) from others.
*/
-#define QUEUE_OFFSET 1
+#define QUEUE_OFFSET 0x7cafe800
#define PIN_GLOBAL_NS 2
#define KEY_IDX 0
@@ -63,6 +63,9 @@ match_q(struct __sk_buff *skb)
if (queue != match_queue)
return TC_ACT_OK;
+
+ /* queue match */
+ skb->cb[1] = 0;
return TC_ACT_UNSPEC;
}
--
2.7.4
